[16] Soddy named this concept isotope meaning ‘same place’. The word ‘isotope’ was initially suggested to him by Margaret Todd. Later, J. J. Thomson showed that non-radioactive elements can also have multiple isotopes.

FRS[2] (2 September 1877 – 22 September 1956) was an Englishradiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also proved the existence of isotopes of certain radioactive elements.[3][4][5][6][7][8][9][10]Frederick Soddy FRS[2] (2 September 1877 – 22 September 1956) was an Englishradiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions. He also proved the existence of isotopes of certain radioactive elements.[3][4][5][6][7][8][9][10]